1. Field of the Invention
This invention relates to three fluid heat transfer apparatus, and particularly to unitary heat exchangers comprising plural heat exchanger cores encountered successively by at least one of the flowing fluids.
2. Description of the Prior Art
Heat transfer apparatus incorporating plural heat exchanger cores have been known heretofore. The routing of fluid flow to and through the cores has been relatively complex, however, and in a structural sense the apparatus tends to assume component form. In some instances, as in aircraft engine accessories and the like, there are advantages to be gained in unitary compact constructions not attainable by use of separate, variously connected component parts. Moreover, a grouping of heat exchanger cores in an in-line relation may result in an elongated structure not adaptable to the physical environment in which it is to be used. It is, still further, desirable when the flow of one fluid is to be controlled by reference to a changing condition of another fluid that elements be in a close coupled relation for quick and simplified response.
To the extent that efforts have been made to remedy problems of the prior art, such efforts have had limited success. It has been particularly noted that in design requirements for a system making alternative use of flowing fuel as a coolant for engine cooling oil and as a coolant for engine cooling air known technology was found insufficient to meet those requirements.